Organic emitting diode and organic light emitting diode display device including the same

ABSTRACT

The present invention provides an organic emitting diode including a first electrode; a second electrode facing the first electrode; an emitting material layer between the first and second electrodes; and an intervening layer between the emitting material layer and the second electrode and including a base material and an electron injection material, wherein the intervening layer contacts the second electrode.

The present application claims the benefit of Korean Patent ApplicationNo. 10-2015-0169502, filed in Korea on Nov. 30, 2015, which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an organic light emitting diode (OLED)display device, and more particularly, to an organic emitting diode andan OLED display device having an improved emitting efficiency and asimple structure.

Discussion of the Related Art

Flat panel display (FPD) devices having a light weight and a thinprofile is widely researched or used instead of a cathode ray tube(CRD).

Among these FPD devices, a liquid crystal display (LCD) device has beenwidely used. However, the LCD device as a non-self emission type displaydevice has disadvantages in brightness, contrast ratio and a viewingangle, the OLED display device is newly researched.

Since the OLED display device is a self-emission type display devicewithout a backlight unit, the OLED display device has advantages inweight and thickness. In addition, the OLED display device has excellentcharacteristic in a viewing angle, contrast ratio, a response time,power consumption, and so on.

FIG. 1 is a diagram illustrating an emission mechanism of an OLEDdisplay device.

Referring to FIG. 1, the OLED display device includes an organicemitting diode. The organic emitting diode may include a first electrode18 as an anode, a second electrode 28 as a cathode and first to fifthorganic layers 30 a, 30 b, 30 c, 30 d and 30 e between the first andsecond electrodes 18 and 28.

The first to fifth organic layers 30 a to 30 e respectively serve as ahole injection layer (HIL) 30 a, a hole transporting layer (HTL) 30 b,an emitting material layer (EML) 30 c, an electron transporting layer(ETL) 30 d and an electron injection layer (EIL) 30 e.

When positive and negative voltages are respectively applied to thefirst and second electrodes 18 and 28, holes and electrons from thefirst and second electrodes 18 and 28 are transported into and combinedin the EML 30 c to form an exciton. The exciton is transited from anexcited state into a ground state (i.e., a stable state) such that thelight is emitted from the organic emitting diode.

In the OLED display device, sub-pixels including the organic emittingdiode are arranged in a matrix shape, and an image is displayed byselectively controlling the sub-pixels.

The OLED display device may be classified into a passive matrix type andan active matrix type. In the active matrix type OLED display device, athin film transistor is turned on and off to select the sub-pixel, andthe emission of the sub-pixel is maintained by a voltage in a storagecapacitor.

Generally, the organic emitting diode is fabricated by a depositionprocess. Namely, a material to be deposited is evaporated in adeposition chamber such that a target layer is deposited on a substrate.

However, in the deposition process, a size of the deposition chambershould be larger than that of the substrate. In addition, additionalspace is required for input/output of the substrate. Accordingly, thereis a limitation in the deposition process for a large-size displaydevice.

To overcome the limitation in the deposition process, a solution processis introduced.

FIG. 2 is a cross-sectional view of the related art organic emittingdiode fabricated by a solution process.

Referring to FIG. 2, the organic emitting diode includes a firstelectrode 18, an emitting part 30 and a second electrode 28 stacked on asubstrate 1.

The emitting part 30 includes an HTL 30 b, an ETL 30 d and an EML 30 ctherebetween. To improve the emitting efficiency, an HIL 30 a is formedbetween the first electrode 18 and the HTL 30 b, and an EIL 30 e isformed between the second electrode 28 and the ETL 30 d.

A part of the emitting part 30 is fabricated by a solution process to beseparated in red, green and blue sub-pixels R, G and B. The HIL 30 a,the HTL 30 b, the EML 30 c are formed by the solution process. However,since the materials of the ETL 30 d and the EIL 30 e have insufficientstability to the solution process, the ETL 30 d and the EIL 30 e areformed by a deposition process.

The ETL 30 d and the EIL 30 e are required to improve the emittingefficiency of the organic emitting diode by efficiently injecting and/ortransporting the electron into the EML 30 c.

On the other hand, the EIL 30 e, which includes sodium fluoride (NaF),may be formed on the EML 30 c without the ETL 30 d. In this instance,the material of the EIL 30 e is diffused into the EML 30 c such that theelectron injection is increased.

However, since a portion of the EML 30 c is changed into a non-emissionpart by diffusion of material of the EIL 30 e, a thickness of the EML 30c should be increased to be over a pre-determined thickness. As aresult, the driving voltage for the organic emitting diode is increased,and there is a limitation in the solution process to increase thethickness of the EML 30 c.

Namely, the Na+ ion of the EIL 30 e is diffused into the EML 30 c suchthat the electron transporting property is increased, while the emittingefficiency is decreased by the Na+ ion diffused portion of the EML 30 c.To prevent the decrease of the emitting efficiency, it is required toincrease the thickness of the EML 30 c. However, the driving voltage forthe organic emitting diode is increased by the thickness increase of theEML 30 c. In addition, since the viscosity of the solution for thesolution process should be increase to increase the thickness of the EML30 c, the coating property is decreased.

SUMMARY

Accordingly, the present invention is directed to an organic emittingdiode and an OLED display device including the same that substantiallyobviate one or more of the problems due to limitations and disadvantagesof the related art.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein, anorganic emitting diode comprises a first electrode; a second electrodefacing the first electrode; an emitting material layer between the firstand second electrodes; and an intervening layer between the emittingmaterial layer and the second electrode and including a base materialand an electron injection material, wherein the intervening layercontacts the second electrode.

In another aspect, an organic light emitting diode display devicecomprises a substrate including a plurality of sub-pixels; a transistorin each sub-pixel; and an organic emitting diode positioned in eachsub-pixel and connected to the transistor, the organic emitting diodeincluding: a first electrode; a second electrode facing the firstelectrode; an emitting material layer between the first and secondelectrodes; and an intervening layer between the emitting material layerand the second electrode and including a base material and an electroninjection material, wherein the intervening layer contacts the secondelectrode.

In another aspect, a method for manufacturing an organic emitting diodecomprises forming a first electrode; forming an emitting material layeron the first electrode; forming an intervening layer including a basematerial and an electron injection material on the emitting materiallayer; and forming a second electrode on the intervening layer tocontact the intervening layer, wherein the emitting material layer andthe intervening layer are formed by solution process.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a diagram illustrating an emission mechanism of an OLEDdisplay device.

FIG. 2 is a cross-sectional view of the related art organic emittingdiode fabricated by a solution process.

FIG. 3 is a schematic block diagram illustrating an OLED display deviceaccording to the present invention.

FIG. 4 is a circuit diagram of a sub-pixel in an OLED display deviceaccording to the present invention.

FIG. 5 is a cross-sectional view of an OLED display device according tothe present invention.

FIG. 6 is a cross-sectional view of an organic emitting diode accordingto the present invention.

FIGS. 7A and 7B are views illustrating a solution process for an organicemitting diode according to the present invention.

FIG. 8 is a graph of a current density according to a voltage in anorganic emitting diode.

FIG. 9 is a graph of a current efficiency according to a current densityin an organic emitting diode.

FIG. 10 is a graph of a light intensity according to a light wavelengthin an organic emitting diode.

FIG. 11 is a cross-sectional view of an OLED display device according tothe present invention.

FIG. 12 is a cross-sectional view of an organic emitting diode accordingto the present invention.

FIG. 13 is an enlarged view of portion “A” in FIG. 12.

FIG. 14 is a graph of a current density according to a voltage in anorganic emitting diode.

DETAILED DESCRIPTION

In the present specification, when a first element is referred to asbeing “on” a second element, it can be directly on the upper surface ofthe second element or a third intervening element may also be present.

Reference will now be made in detail to the preferred embodiments,examples of which are illustrated in the accompanying drawings.

FIG. 3 is a schematic block diagram illustrating an OLED display deviceaccording to the present invention.

Referring to FIG. 3, the OLED display device includes an image treatingunit 115, a data conversion unit 114, timing controller 113, a datadriver 112, a gate driver 111 and a display panel 110.

The image treating unit 115 performs various image treating processes,e.g., setting a gamma voltage for providing a maximum brightnessaccording to an average image level, using the RGB data signals andoutputs the treated RGB data. In addition, the image treating unit 115outputs a driving signal including at least one of a vertical syncsignal (Vsync), a horizontal sync signal (Hsync), a data enable signal(DES) and a clock signal (CLK).

The timing controller 113 receives the driving signal including at leastone of the Vsync, the Hsync, the DES and the CLK. The timing controller113 outputs a gate timing control signal GCS for controlling anoperation timing of the gate driver 111 and a data timing control signalDCS for controlling an operation timing of the data driver 112 accordingto the driving signal. In addition, the timing controller 113 outputs adata signal DATA corresponding to the GCS and the DCS.

In response to the DCS, the data driver 112 is performed a samplingprocess of the DATA from the timing controller 113 to output a gammareference voltage. The data driver 112 outputs modified DATA to the datalines DL1 to DLm. The data driver 112 includes an integrated circuit(IC).

In response to the GCS from the timing controller 113, the gate driver111 shifts a level of a gate voltage and outputs a gate signal. The gatedriver 111 outputs the gate signal to the gate lines GL1 to GLn. Thegate driver 111 includes an IC or is installed on the display panel 110in a gate-in-panel (GIP) type.

The display panel 110 may includes a red sub-pixel SPr, a greensub-pixel SPg and a blue sub-pixel SPb. Namely, one pixel P may includethe red, green and blue sub-pixels SPr, SPg and SPb, but it is notlimited thereto. For example, the pixel P may further include a whitesub-pixel.

FIG. 4 is a circuit diagram of a sub-pixel in an OLED display deviceaccording to the present invention.

In FIG. 4, the sub-pixel includes a switching transistor, a drivingtransistor and a capacitor with an organic emitting diode. Namely, thesub-pixel has a 2-transistor-1-capacitor (2T1C) structure.Alternatively, the sub-pixel may have a 3T1C structure, a 4T2C structureor a 5T2C structure.

Referring to FIG. 4, in the OLED display device, a sub-pixel region isdefined by a gate line GL, a data line DL and a power line VDDL. Thegate line GL extends along a first direction, and each of the data lineDL and the power line VDDL extend along a second direction to cross thegate line GL. The data line DL and the power line VDDL are spaced apartfrom each other to be parallel to each other.

In each sub-pixel, the switching transistor SW, the driving transistorDR, the capacitor Cst, a compensation circuit CC and the organic lightemitting diode OLED.

The organic emitting diode is operated to emit the light according to adriving current through the driving transistor DR. The switchingtransistor SW is switched to store the data signal, which is providedthrough the data line DL according to the gate signal provided throughthe data line GL, into the capacitor Cst as a data voltage. The drivingtransistor DR is operated to provide the signal of the power line VDDLto the ground GND according to the data voltage in the capacitor Cst.The threshold voltage of the driving transistor DR is compensated by thecompensation circuit CC. For example, the compensation circuit CC mayinclude at least one transistor and at least one capacitor, but it isnot limited thereto.

The OLED display device may be classified into a top emission type, abottom emission type or a dual emission type according to an emittingdirection of the light.

FIG. 5 is a cross-sectional view of an OLED display device according tothe present invention, and FIG. 6 is a cross-sectional view of anorganic emitting diode according to the present invention.

In FIG. 5, one pixel includes the red, green and blue (RGB) sub-pixels.The OLED display device in FIG. 5 will be explained in the bottomemission type. Namely, the light from the organic emitting diode passesthrough a substrate 101 to display image. Alternatively, the light fromthe organic emitting diode may pass a second electrode 128 (top emissiontype). In addition, the light from the organic emitting diode may passboth the substrate 101 and the second electrode 128 (dual emissiontype).

In FIG. 5, the OLED display device includes a thin film transistor of acoplanar structure, but it is not limited thereto.

Referring to FIGS. 5 and 6, the OLED display device includes atransistor TFT on the substrate 101 and an organic emitting diode OLEDover the substrate 101.

For example, the substrate 101 may be divided into the red, green andblue sub-pixels R, G and B, and the R, G and B sub-pixels may beregularly repeated in each line direction or in a diagonal direction.

The transistor TFT as a driving thin film transistor includes asemiconductor layer 124, a gate electrode 121, a source electrode 122and a drain electrode 123.

The semiconductor layer 124 is formed on the substrate 101 being formedof an insulating material such as a transparent plastic or a transparentpolymer film.

The semiconductor layer 124 may be formed of amorphous silicon, apoly-silicon, an oxide semiconductor or an organic semiconductor.

A buffer layer (not shown) may be formed between the substrate 101 andthe semiconductor layer 124. The transistor TFT is protected fromimpurities, e.g., alkali ion, from the substrate 101 by the bufferlayer.

A gate insulating layer 125 a is formed on the semiconductor layer 124.For example, the gate insulating layer 125 a may be formed of aninorganic insulating material such as silicon oxide or silicon nitride.The gate electrode 121, a gate line (not shown) and a first capacitorelectrode (not shown) are formed on the gate insulating layer 125 a. Thegate electrode 121 corresponds to the semiconductor layer 124.

Each of the gate electrode 121, the gate line and the first capacitorelectrode is formed of a first metallic material having low resistance.For example, each of the gate electrode 121, the gate line and the firstcapacitor electrode may be formed of at least one of aluminum (Al),copper (Cu), molybdenum (Mo), chromium (Cr), gold (Au), titanium (Ti),nickel (Ni), neodymium (Nd) and their alloys and may have asingle-layered structure or a multi-layered structure.

An interlayer insulating layer 125 b, which is formed of an inorganicmaterial such as silicon oxide or silicon nitride, is formed on the gateelectrode 121, the gate line and the first capacitor electrode, and adata line (not shown), a power line (not shown), the source electrode122, the drain electrode 123 and a second capacitor electrode (notshown) are formed on the interlayer insulating layer 125 b.

The source and drain electrodes 122 and 123 are spaced apart from eachother and electrically connected to the semiconductor layer 124,respectively. For example, first and second semiconductor contact holesare formed through the gate insulating layer 125 a and the interlayerinsulating layer 125 b to expose both ends of the semiconductor layer124, and the source and drain electrodes 122 and 123 contact thesemiconductor layer 124 through the first and second semiconductorcontact holes, respectively.

The second capacitor electrode overlaps the first capacitor electrodewith the interlayer insulating layer 125 b therebetween to form astorage capacitor.

Each of the data line, the power line, the source electrode 122, thedrain electrode 123 and the second capacitor electrode may be formed ofa second metallic material having low resistance. For example, each ofthe data line, the power line, the source electrode 122, the drainelectrode 123 and the second capacitor electrode may be formed of atleast one of Al, Cu, Mo, Cr, Au, Ti, Ni, Nd and their alloys and mayhave a single-layered structure or a multi-layered structure.

A passivation layer (or a planarization layer) 125 c is formed over thesubstrate 101 including the data line, the power line, the sourceelectrode 122, the drain electrode 123 and the second capacitorelectrode, and an overcoat layer 125 d is formed on the passivationlayer 125 c. A drain contact hole exposing the drain electrode 123 isformed through the overcoat layer 125 d and the passivation layer 125 c.

The passivation layer 125 c may be formed of an organic material, aninorganic material or their mixture. When the passivation layer 125 chas a function of the overcoat layer, the overcoat layer 125 d may beomitted.

The organic emitting diode OLED including a first electrode 118, anemitting part 130 and a second electrode 128 is formed on the overcoatlayer 125 d.

The organic emitting diode OLED is electrically connected to the drivingthin film transistor TFT. In more detail, the first electrode 118 on theovercoat layer 125 d is electrically connected to the drain electrode123 of the driving thin film transistor TFT through the drain contacthole.

The first electrode 118 providing a current (or a voltage) to theemitting part 130 defines an emission region of a pre-determined area.

The first electrode 118 includes a relatively high work function toserve as an anode. For example, the first electrode 118 may include atransparent conductive material, e.g., indium-tin-oxide (ITO) orindium-zinc-oxide (IZO), but it is not limited thereto.

In FIG. 5, the first electrodes 118 in the R, G and B sub-pixel areseparated from each other. Alternatively, the first electrodes 118 inthe R, G and B sub-pixel are integrated to have one-body.

A bank 125 e is formed over the substrate 101 including the firstelectrode 118. The bank 125 e covers edges of the first electrode 125 eto surround the sub-pixel. Namely, the bank 125 e has an opening incorrespondence to a center of the first electrode 118. The bank 125 emay include an organic material. The bank 125 e may be formed of aphoto-sensitive material including a black pigment to serve as a lightshielding element.

The emitting part 130 and the second electrode 128 are sequentiallyformed over the substrate 101 including the bank 125 e.

The emitting part 130 is disposed between the first and secondelectrodes 118 and 128. The holes from the first electrode 118 and theelectrons from the second electrode 128 are combined in the emittingpart 130 such that the emitting part 130 emits.

The emitting part 130 includes an HTL 130 b as an auxiliary layer and anEML 130 c as a light emitting layer. The HTL 130 b may have asingle-layered structure or a multi-layered structure. To improve theemitting efficiency, the emitting part 130 may further include an HIL130 a between the first electrode 118 and the HTL 130 b.

The EML 130 includes a first emitting layer 130 c′ having an improvedinterface property with the HTL 130 b and a second emitting layer 130 c″(referred to as “intervening layer” in another embodiment) having animproved electron injection property. An electron injection material isadded into the emitting material of the EML 130 to form the secondemitting layer 130 c″.

Namely, the first emitting layer 130 c′ includes a material improvingthe interface property with the HTL 130 b to increase a lifetime of theorganic emitting diode OLED. On the other hand, the second emittinglayer 130 c″ includes the emitting injection material to have animproved electron injection property such that the emitting efficiencyof the organic emitting diode OLED is increased.

The electron injection material may have a concentration (or density)gradient in the second emitting layer 130 c″ as explained with FIG. 13.Namely, the electron injection material in a lower portion, which isadjacent to the first emitting layer 130 c′, of the second emittinglayer 130 c″ may have a first concentration (or density) with respect tothe emitting material in the second emitting layer 130 c″, and theelectron injection material in an upper portion, which is adjacent tothe second electrode 128, of the second emitting layer 130 c″ may have asecond concentration (or density), which is larger than the firstconcentration (or density), with respect to the emitting material in thesecond emitting layer 130 c″.

The second emitting layer 130 c″ is formed by a solution process using asolvent being damage-less to the first emitting layer 130 c′.Accordingly, since the electron injection property is improved by thesecond emitting layer 130 c″, the emitting efficiency of the organicemitting diode OLED is increased without the ETL and the EIL.

For example, the electron injection material may include water-solubleor fat-soluble alkali metal. When the first emitting layer 130 c′ isformed using an organic solvent (i.e., fat-soluble), the second emittinglayer 130 c″ is formed using the water-soluble material to preventdamages on the first emitting layer 130 c′. Alternatively, when thefirst emitting layer 130 c′ is formed using the water-soluble solvent,the second emitting layer 130 c″ is formed using the organic solvent(i.e., fat-soluble solvent) to prevent damages on the first emittinglayer 130 c′.

The second emitting layer 130 c″ has a relatively low lowest unoccupiedmolecular orbital (LUMO) energy level, e.g., about 3.0 eV to 2.6 eV, anda triplet energy level (T1) of about 2.0 eV to about 2.5 eV. Inaddition, the second emitting layer 130 c″ has an electron mobility ofabout 10⁻⁶ cm²/Vs to about 10⁻⁴ cm²/Vs.

In the organic emitting diode OLED of the present invention, since theelectron from the second electrode 128 is securely transported into theEML 130 c without the ETL and the EIL, the OLED has sufficient emittingefficiency and lifetime with a simple structure.

Namely, the problems, which is generated by diffusion of a material inthe EIL and/or ETL into the EML in the related art organic emittingdiode, is prevented in the organic emitting diode OLED and the OLEDdisplay device.

The emitting part 130 is fabricated in the R, G and B sub-pixels by asolution process. Namely, a low molecular or high molecular polymermaterial is coated on the first electrode 130 to form the emitting part130.

In the emitting part 130, the HIL 130 a may be omitted. Alternatively,the HIL 130 a and the HTL 130 b may be formed by one layer with a mixedmaterial. In addition, at least one of the HIL 130 a and the HTL 130 bmay have at least double-layered structure.

The EML 130 c in the R, G and B sub-pixels includes a fluorescentemitting material or a phosphorescent emitting material. In addition,the EML 130 c may include at least one host and at least one dopant.

The solution process for the emitting part 130 may be one of an injectprinting process, a nozzle printing process, a transferring process, athermal jet printing process a roll printing process, a gravure printingprocess and a spin coating process. However, it is not limited thereto.

The solution process can be performed without a mask or a chamber.Accordingly, since the solution process is simpler and the process costis cheaper in comparison to the deposition process, the process time andthe production cost for the organic emitting diode and the OLED displaydevice are reduced.

In addition, since the ETL and the EIL, which are fabricated by thedeposition process, can be omitted, the production yield of the organicemitting diode and the OLED display device is increased.

FIGS. 7A and 7B are views illustrating a solution process for an organicemitting diode according to the present invention.

FIG. 7A shows the inkjet printing process. As shown in FIG. 7A, aninkjet apparatus (not shown) including a head 140 is disposed over thesubstrate 101, and an ink is printed on the substrate 140. The head 140includes a jetting hole for ink jetting.

In this instance, the head 140 or the substrate 101 is moved along atleast one direction during the ink jetting such that the ink 145 isselectively printed in the sub-pixels.

In the nozzle printing process, at least one nozzle having a slit shapeis used to print the ink on the substrate. In comparison to the inkjetprinting process, the nozzle printing process is adequate to a largesize substrate. For example, a layer is printed over the substrate 101,where the bank is formed, by an entire-surface nozzle printing process.

FIG. 7B shows the roll printing process. As shown in FIG. 7B, a mainroller 150, where a pattern 155 is formed, is rotated on the substrate101 to form a printing pattern. In this instance, an auxiliary roller151 is connected to a head providing a printing solution such that theprinting solution is continuously provided into the pattern 155 on themain roller 150. Without the pattern 155, the material may be printed orcoated on an entire surface of the substrate 101.

Referring again to FIGS. 5 and 6, the second electrode 128 is formed onthe emitting part 130, and the electron is provided from the secondelectrode 128 into the emitting part 130.

The second electrode 128 is formed on an entire surface of the substrate101. Namely, the second electrodes 128 in the sub-pixels are integratedas one-body.

FIG. 8 is a graph of a current density according to a voltage in anorganic emitting diode, FIG. 9 is a graph of a current efficiencyaccording to a current density in an organic emitting diode, and FIG. 10is a graph of a light intensity according to a light wavelength in anorganic emitting diode. The graph in FIG. 10 is obtained in the redsub-pixel.

In FIGS. 8 to 10, the organic emitting diode of the comparative example1 (Com1) includes an electron injection layer (EIL) without an electrontransporting layer (ETL), and the organic emitting diode of thecomparative example 2 (Com2) includes both an EIL and an ETL.

Referring to FIG. 8, a current density (Cd) in the organic emittingdiode of “Com1” is lower at the same voltage than that in the organicemitting diode of “Com2”. A current density (Cd) of the organic emittingdiode of the example 1 (Ex1) including the first and second emittinglayers 130 c′ and 130 c″ without the EIL and the ETL is higher than thatin the organic emitting diode of “Com1” and “Com2”. Namely, the drivingefficiency of the organic emitting diode of the present invention isimproved, and the driving voltage of the organic emitting diode of thepresent invention is decreased.

Referring to FIG. 9, a current efficiency (Ce) of the organic emittingdiode of the example 1 (Ex1) is higher than that in the organic emittingdiode of “Com1” and “Com2”. It means that the lifetime of the organicemitting diode in the present invention is increased.

Referring to FIG. 10, in the organic emitting diode of “Com1”, theemitting injection material in the EIL is diffused into the EML suchthat an emission region is shifted. As a result, there is a peak in awavelength above a red wavelength, i.e., 600˜650 nm). However, in theorganic emitting diode of “Com1” and “Ex1”, the peak shift problem isreduced such that a color purity is improved.

FIG. 11 is a cross-sectional view of an OLED display device according tothe present invention, and FIG. 12 is a cross-sectional view of anorganic emitting diode according to the present invention.

Referring to FIGS. 11 and 12, the OLED display device includes atransistor TFT on the substrate 201 and an organic emitting diode OLEDover the substrate 201.

The substrate 201 may be divided into the red, green and blue sub-pixelsR, G and B, and the R, G and B sub-pixels may be regularly repeated. Forexample, the substrate 201 is formed of an insulating material such as atransparent plastic or a transparent polymer film to be flexible.

The transistor TFT as a driving element includes a semiconductor layer224, a gate electrode 221, a source electrode 222 and a drain electrode223.

The semiconductor layer 224 is formed on the substrate 201. For example,the semiconductor layer 224 may be formed of amorphous silicon, apoly-silicon, an oxide semiconductor or an organic semiconductor.

A buffer layer (not shown) may be formed between the substrate 201 andthe semiconductor layer 224. The transistor TFT is protected fromimpurities, e.g., alkali ion, from the substrate 201 by the bufferlayer.

A gate insulating layer 225 a is formed on the semiconductor layer 224.For example, the gate insulating layer 225 a may be formed of aninorganic insulating material such as silicon oxide or silicon nitride.

The gate electrode 221, a gate line (not shown) and a first capacitorelectrode (not shown) are formed on the gate insulating layer 225 a. Thegate electrode 221 corresponds to the semiconductor layer 224.

Each of the gate electrode 221, the gate line and the first capacitorelectrode is formed of a first metallic material having low resistance.For example, each of the gate electrode 221, the gate line and the firstcapacitor electrode may be formed of at least one of aluminum (Al),copper (Cu), molybdenum (Mo), chromium (Cr), gold (Au), titanium (Ti),nickel (Ni), neodymium (Nd) and their alloys and may have asingle-layered structure or a multi-layered structure.

An interlayer insulating layer 225 b is formed on the gate electrode221, the gate line and the first capacitor electrode. For example, theinterlayer insulating layer 225 b may be formed of an inorganic materialsuch as silicon oxide or silicon nitride,

A data line (not shown), a power line (not shown), the source electrode222, the drain electrode 223 and a second capacitor electrode (notshown) are formed on the interlayer insulating layer 225 b.

The source and drain electrodes 222 and 223 are spaced apart from eachother and electrically connected to the semiconductor layer 224,respectively. For example, first and second semiconductor contact holesare formed through the gate insulating layer 225 a and the interlayerinsulating layer 225 b to expose both ends of the semiconductor layer224, and the source and drain electrodes 222 and 223 contact thesemiconductor layer 224 through the first and second semiconductorcontact holes, respectively.

The second capacitor electrode overlaps the first capacitor electrodewith the interlayer insulating layer 225 b therebetween to form astorage capacitor.

Each of the data line, the power line, the source electrode 222, thedrain electrode 223 and the second capacitor electrode may be formed ofa second metallic material having low resistance. For example, each ofthe data line, the power line, the source electrode 222, the drainelectrode 223 and the second capacitor electrode may be formed of atleast one of Al, Cu, Mo, Cr, Au, Ti, Ni, Nd and their alloys and mayhave a single-layered structure or a multi-layered structure.

Although not shown, a switching element, which has substantially thesame structure as the transistor TFT, is further formed in the R, G andB sub-pixels. The switching element is electrically connected to thegate line, the data line and the transistor TFT.

A passivation layer (or a planarization layer) 225 c is formed over thesubstrate 201 including the data line, the power line, the sourceelectrode 222, the drain electrode 223 and the second capacitorelectrode, and an overcoat layer 225 d is formed on the passivationlayer 225 c. A drain contact hole exposing the drain electrode 223 isformed through the overcoat layer 225 d and the passivation layer 225 c.

Each of the passivation layer 225 c and the overcoat layer 22 d isformed of an inorganic insulating material, e.g., silicon oxide orsilicon nitride, or an organic insulating material, e.g., photo-acryl.One of the passivation layer 225 c and the overcoat layer 22 d may beomitted.

The organic emitting diode OLED including a first electrode 218, anemitting part 230 and a second electrode 228 is formed on the overcoatlayer 225 d. The organic emitting diode OLED is electrically connectedto the transistor TFT.

The first electrode 218 is formed on the overcoat layer 225 d to beseparated in the R, G and B sub-pixel and is electrically connected tothe drain electrode 223 of the transistor TFT through the drain contacthole.

The first electrode 218 providing a current (or a voltage) to theemitting part 230 defines an emission region of a pre-determined area.

The first electrode 218 includes a relatively high work function toserve as an anode. For example, the first electrode 218 may include atransparent conductive material, e.g., indium-tin-oxide (ITO) orindium-zinc-oxide (IZO), but it is not limited thereto.

In the top emission type OLED display device, a reflection electrode ora reflection layer may be formed under and/or on the first electrode218. For example, each of the reflection electrode or the reflectionlayer may include aluminum-paladium-copper (APC) alloy. In other words,the first electrode 218 may have a double-layered structure includingthe transparent conductive electrode and the reflection electrode orlayer under the transparent conductive electrode or a triple-layeredstructure including the transparent conductive electrode and thereflection electrode or layer under and the transparent conductiveelectrode.

A bank 225 e is formed over the substrate 201 including the firstelectrode 218. The bank 225 e covers edges of the first electrode 225 eto surround the sub-pixel. Namely, the bank 225 e has an opening incorrespondence to a center of the first electrode 218. The bank 225 emay include an organic material. The bank 225 e may be formed of aphoto-sensitive material including a black pigment to serve as a lightshielding element.

The emitting part 230 and the second electrode 228 are sequentiallyformed over the substrate 201 including the bank 225 e.

The emitting part 230 is disposed between the first and secondelectrodes 218 and 228. The holes from the first electrode 218 and theelectrons from the second electrode 228 are combined in the emittingpart 230 such that the emitting part 230 emits.

The emitting part 230 includes an EML 230 c and an ETL 230 d between theEML 230 and the second electrode 228 without an electron injectionlayer. Namely, the ETL 230 d contacts the second electrode 228. Inaddition, the emitting part 230 may further include an HIL 230 a and anHTL 230 b sequentially stacked on the first electrode 218 and under theEML 230 c.

The ETL 230 d (referred to as “intervening layer” in another embodiment)includes an electron transporting material (not shown) and an electroninjection material 232 (of FIG. 13) having an excellent electronproperty. In other words, the electron injection material 232 is dopedinto the ETL 230 d.

The electron transporting material has a LUMO energy level of about 3.0eV to about 2.0 eV and an electron mobility of about 10⁻⁵ cm²Ns to about10⁻³ cm²/Vs. In addition, the ETL 230 d, where the electron injectionmaterial 232 is doped, has a triplet energy (T1) level of about 2.0 eVto about 2.5 eV. For example, the electron injection material 232 mayinclude water-soluble or fat-soluble alkali metal.

When the emitting material layer 230 c′ is formed using an organicsolvent (i.e., fat-soluble), the electron transporting layer 230 d isformed using the water-soluble material to prevent damages on theemitting material layer 230 c′. Alternatively, when the emittingmaterial layer 230 c′ is formed using the water-soluble solvent, theelectron transporting layer 230 d is formed using the organic solvent(i.e., fat-soluble solvent) to prevent damages on the emitting materiallayer 230 c′.

The electron injection material 232 has a concentration gradient (or adensity gradient) in a vertical direction.

Namely, referring to FIG. 13, which an enlarged view of a portion “A” inFIG. 12, the electron injection material 232 has a first concentration(or a first density) in a lower portion 240, which is adjacent to theEML 230 c, of the ETL 230 d and a second concentration (or a seconddensity) in an upper portion 250, which is adjacent to the secondelectrode 228, of the ETL 230 d. The second concentration is larger thanthe first concentration.

For example, the electron injection material 232 has a first weight % ofabout 150 in the upper portion with respect to the electron transportingmaterial and a second weight % of about 50 in the lower portion withrespect to the electron transporting material.

In addition, the electron injection material 232 may have aconcentration gradient in each of the lower and upper portions 240 and250. Namely, in each of the lower and upper portions 240 and 250, theconcentration (or the density) of the electron injection material 232 isreduced in a direction from the upper portion 250 to the lower portion240. Alternatively, the electron injection material 232 may have thesame concentration (or the density) in each of the lower and upperportions 240 and 250.

The ETL 230 d includes the electron injection material 232 such that theelectron injection property of the ETL 230 d is increased. Accordingly,without the EIL, the organic emitting diode has a simple structure and athin profile.

In addition, since the electron injection material 232 has theconcentration gradient in the ETL 230 d, the diffusion of the electroninjection material 232 into the EML 230 c is minimized.

To provide a desired electron injection property in the ETL 230 d, theelectron injection material 232 should be doped into the ETL 230 d in apre-determined concentration. In the organic emitting diode of thepresent invention, since the electron injection material 232 has arelatively low concentration in the lower portion 240, which is adjacentto the EML 230 c, of the ETL 230 d, the diffusion of the electroninjection material 232 into the EML 230 c is minimized. With the firstconcentration (>0) of the electron injection material 232 in the lowerportion 240 of the ETL 230 d, there is an advantage in the emittingefficiency by the electron injection material but there is nodisadvantage in the emitting property by the diffusion of the electroninjection material 232 into the EML 230 c.

In other words, in the organic emitting diode of the present invention,the electron injection property of the ETL 230 d is increased by dopingthe electron injection material, and the problem in the lifetime and theemitting efficiency is prevented by the concentration gradient of theelectron injection material 232.

An ITO layer and an electron blocking layer (Liq, 1 nm) are sequentiallydeposited on a glass substrate, and an electron transporting layer (50nm), where an electron injection material is doped in gradient, and acathode (Al, 100 nm) are sequentially stacked on the electron blockinglayer (example 2 (Ex2), electron only device).

An ITO layer and an electron blocking layer (Liq, 1 nm) are sequentiallydeposited on a glass substrate, and an electron transporting layer (50nm) without an electron injection material and a cathode (Al, 100 nm)are sequentially stacked on the electron blocking layer (comparativeexample 3 (Com3), electron only device).

As shown in FIG. 14, which is a graph of a current density according toa voltage in an organic emitting diode, the current density in theorganic emitting diode of “Ex2”, where the electron injection materialis doped into the electron transporting layer to have a concentrationgradient, is higher than that in the organic emitting diode of “Com3”.Namely, the emitting efficiency of the organic emitting diode and theOLED display device is improved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An organic emitting diode, comprising: a firstelectrode; a second electrode facing the first electrode; an emittingmaterial layer between the first and second electrodes; and anintervening layer between the emitting material layer and the secondelectrode and including a base material and an electron injectionmaterial, wherein the intervening layer contacts the second electrode.2. The organic emitting diode according to claim 1, wherein the basematerial is a host material of the emitting material layer.
 3. Theorganic emitting diode according to claim 2, wherein the interveninglayer has a LUMO energy level of about 3.0 eV to 2.6 eV and a tripletenergy level of about 2.0 eV to about 2.5 eV.
 4. The organic emittingdiode according to claim 2, wherein the intervening layer has anelectron mobility of about 10⁻⁶ cm²/Vs to about 10⁻⁴ cm²/Vs.
 5. Theorganic emitting diode according to claim 1, wherein the base materialis an electron transporting material.
 6. The organic emitting diodeaccording to claim 5, wherein the electron transporting material has aLUMO energy level of about 3.0 eV to 2.0 eV and the electrontransporting layer has a triplet energy level of about 2.0 eV to about2.5 eV.
 7. The organic emitting diode according to claim 5, wherein theelectron transporting material has an electron mobility of about 10⁻⁵cm²/Vs to about 10⁻³ cm²/Vs.
 8. The organic emitting diode according toclaim 1, wherein the electron injection material has a first density ina lower portion, which is adjacent to the emitting material layer, ofthe intervening layer and a second density, which is larger than thefirst density, in an upper portion, which is adjacent to the secondelectrode, of the intervening layer.
 9. The organic emitting diodeaccording to claim 1, wherein the electron injection material includesan alkali metal.
 10. An organic light emitting diode display device,comprising: a substrate including a plurality of sub-pixels; atransistor in each sub-pixel; and an organic emitting diode positionedin each sub-pixel and connected to the transistor, the organic emittingdiode including: a first electrode; a second electrode facing the firstelectrode; an emitting material layer between the first and secondelectrodes; and an intervening layer between the emitting material layerand the second electrode and including a base material and an electroninjection material, wherein the intervening layer contacts the secondelectrode.
 11. The organic light emitting diode display device accordingto claim 10, wherein the base material is a host material of theemitting material layer.
 12. The organic light emitting diode displaydevice according to claim 11, wherein the intervening layer has a LUMOenergy level of about 3.0 eV to 2.6 eV and a triplet energy level ofabout 2.0 eV to about 2.5 eV.
 13. The organic light emitting diodedisplay device according to claim 11, wherein the intervening layer hasan electron mobility of about 10⁻⁶ cm²/Vs to about 10⁻⁴ cm²/Vs.
 14. Theorganic light emitting diode display device according to claim 10,wherein the base material is an electron transporting material.
 15. Theorganic light emitting diode display device according to claim 14,wherein the electron transporting material has a LUMO energy level ofabout 3.0 eV to 2.0 eV and the electron transporting layer has a tripletenergy level of about 2.0 eV to about 2.5 eV.
 16. The organic lightemitting diode display device according to claim 14, wherein theelectron transporting material has an electron mobility of about 10⁻⁵cm²/Vs to about 10⁻³ cm²/Vs.
 17. The organic light emitting diodedisplay device according to claim 10, wherein the electron injectionmaterial has a first density in a lower portion, which is adjacent tothe emitting material layer, of the intervening layer and a seconddensity, which is larger than the first density, in an upper portion,which is adjacent to the second electrode, of the intervening layer. 18.The organic light emitting diode display device according to claim 10,wherein the electron injection material includes an alkali metal.
 19. Amethod for manufacturing an organic emitting diode, comprising: forminga first electrode; forming an emitting material layer on the firstelectrode; forming an intervening layer including a base material and anelectron injection material on the emitting material layer; and forminga second electrode on the intervening layer to contact the interveninglayer, wherein the emitting material layer and the intervening layer areformed by solution process.
 20. The method according to claim 19,wherein the base material is a host material of the emitting materiallayer or an electron transporting material.
 21. The method according toclaim 20, wherein the solution process includes an inject printingprocess, a nozzle printing process, a transferring process, a thermaljet printing process a roll printing process, a gravure printing processand a spin coating process.
 22. The method according to claim 20,wherein the emitting material layer is formed using an organic solvent;and the intervening layer is formed using a water-soluble material inwhich a water-soluble or fat soluble alkali metal as the electroninjection material is dispersed.
 23. The method according to claim 20,wherein the emitting material layer is formed using a water-solublematerial; and the intervening layer is formed using an organic solventin which a water-soluble or fat soluble alkali metal as the electroninjection material is dispersed.